The present invention relates to a projection image display apparatus that displays images by projecting them onto the front of a screen or from the rear of the screen. The invention also relates to a projection optical unit used for such a display apparatus.
An image display apparatus that uses a projection optical unit to provide an enlarged on-screen projection of the images displayed by an image display element is required to obtain large enough an enlarged image on the screen, while at the same time, shortening the projection distance. A projection optical unit is known that is adapted to implement the above by projecting an image in enlarged form from an oblique direction with respect to a screen, as described in, for example, Japanese Patent Laid-Open No. Hei 5-134213 (Patent document 1), 2000-162544 (Patent document 2), 2002-357768 (Patent document 3).